聚苯乙烯论文碳纳米管选择性分散及其诱导不相容共混物结晶的研究

1、聚苯乙烯论文：碳纳米管选择性分散及其诱导不相容共混物结晶的研究【中文摘要】聚合物共混改性可以使单一聚合物的性能优化组合,并且获得一些特殊性能,成为开发新型高分子材料的有效途径。对于大部分的聚合物在热力学上是不相容的,不相容共混物增容改性的方法很多,添加无机纳米填料是一种实际有效的方法。碳纳米管(Carbon Nanotubes, CNTs)自从被发现以来,由于其具有优异的力学、导电、导热特性而备受关注,此外碳纳米管对结晶聚合物是很好的成核剂,少量的碳纳米管可以诱导结晶,降低结晶活化能,提高结晶速率。聚苯乙烯(Polystyrene, PS).聚丙烯(Polypropylene, PP)、聚对苯

2、二甲酸乙二醇酯(Polyethylene terephthalate, PET)在生活、工程应用上很广泛,对其进行共混改性具有现实意义。本论文以PS/PP、PS/PET不相容共混物作为研究对象,多壁碳纳米管(Multi-Walled Nanotubes, MWCNTs)做为无机纳米填料来制备纳米复合材料。首先对碳纳米管进行化学改性,改善其与基体之间的相互作用,控制其在复合材料中的分布；研究了加工共混条件、增容剂的添加、界面条件等对碳纳米管在不相容共混物中选择性分布的影响,并进一步探讨了碳纳米管的分布对结晶相的结晶行为以及对复合材料微观相形貌的影响。主要研究结果如下：(1)对碳纳米管先酸化处理,

3、然后与马来酸酐反应,使其表面接枝上羰基、羟基、羧基等活性基团,得到改性的多壁碳纳米管(Functionalized Multi-walled Carbon Nanotubes, F-MWCNTs)。(2)把F-MWCNTs加入到PS/PP不相容共混物中,PS与F-MWCNTs通过溶液法配制母料,再与其他组分挤出注塑制备复合材料。对PP结晶行为的研究发现,PS/PP共混物中,PP在低温、高温处出现两个结晶峰,有分级结晶现象,但添加F-MWCNTs后PP只有一个高温结晶峰,分级结晶现象消失；同时,PS/PP/F-MWCNTs复合材料中PP相的结晶温度比PS/PP共混物中PP相的结晶温度高,复合材料

4、中PP相的结晶温度随着PP含量的增加而逐渐提高,表明F-MWCNTs跟PP间相互作用更强,F-MWCNTs从PS相迁移到了PP相中,F-MWCNTs作为很好的异相成核剂诱导PP结晶。另外动态力学分析(Dynamic Mechanical Analysis, DMA)数据表明,复合材料中PS、PP的玻璃化温度有所降低,说明F-MWCNTs充当了增塑剂的作用。扫描电子显微镜(Scanning Electron Microscope, SEM)对复合材料相形貌研究表明F-MWCNTs的引入在一定程度上促进了PS/PP相形貌从“海岛”相向双连续相的转变。(3)在80PP/20PS不相容共混物中添加马来

5、酸酐接枝苯乙烯-乙烯-丁二烯-苯乙烯(Maleic Anhydride Grafted Styrene-Ethylene-Butylenes-Styrene, SEBS-MA)作为增容剂,降低了两相的界面张力,增强了两相间的粘结力,分散相粒径变小,分散更均匀。同时研究了加工共混条件以及增容剂对F-MWCNTs在复合材料中选择性分布情况的影响。以PP/F-MWCNTs作为母料制备的纳米复合材料,SEBS-MA加入后PP的结晶温度降低,表明F-MWCNTs与SEBS-MA的相互作用比较强,部分的F-MWCNTs被SEBS-MA诱导而从PP相中迁移出来；DMA表征发现PS玻璃化温度没有变化,F-MW

6、CNTs并没有迁移到PS相中。以PS/F-MWCNTs作为母料制备的纳米复合材料,各个组分中PP的结晶温度变化不大,DMA结果发现PP玻璃化温度也没有变化,说明F-MWCNTs没有迁移到PP相中,主要还是分布在PS相中,SEBS-MA的存在可以阻止F-MWCNTs的迁移。以PP-MA为基体,PS/F-MWCNTs为母料制备的纳米复合材料,PP-MA结晶行为的研究也说明SEBS-MA与F-MWCNTs之间的相互作用力比PP-MA与F-MWCNTs之间的作用力更强。(4)制备了PS/PET/F-MWCNTs纳米复合材料,通过热力学润湿系数计算表明F-MWCNTs倾向于分布在PET相中。对复合材料中

7、PET的结晶行为的研究表明F-MWCNTs诱导PET结晶,起到了很好的异相成核作用,F-MWCNTs从PS相往PET相迁移；通过SEM直观的反映了F-MWCNTs主要分布在PET相中及两相界面,验证了F-MWCNTs在复合材料中的分布情况。【英文摘要】Polymer blending is a convenient and efficient route for the development of new polymeric materials, which can combine the excellent and special properties of the constituent

8、 polymers. Many polymer blends are immiscible and their blends exhibit poor mechanical properties. Among various techniques used to compatibilize polymer blends, adding inorganic nanofillers is proved to be one of the most efficient methods. Since their discovery, carbon nanotubes (CNTs) attracted t

9、remendous attention due to their superior mechanical, electrical and thermal properties. CNTs have been proved to be a good nucleating agent for crystallization of polymers. The addition of a few CNTs in semicrystalline polymer can efficiently promote the crystallization by decreasing the nucleation

10、 activation energy and accelerating crystallization rate. Polystyrene (PS), polypropylene (PP) and polyethylene terephthalate (PET) are important engineering polymers used in a wide variety of applications, and melt blending of them are of practical significance. In this research, nanocomposites of

11、PS/PP and PS/PET containing Multi-walled nanotubes (MWCNTs) were mainly prepared by direct melt blending. MWCNTs were firstly functionalized to improve the adhesion with polymer matrices, so we can control the localization and dispersion of MWCNTs in immiscible polymer blends. The selective localiza

12、tion of MWCNTs in nanocomposites was realized by the different blending sequences, the use of compatibilizer, etc. Furthermore, the effect of selective localization of MWCNTs on the crystallization and morphology behaviors of nanocomposites were discussed. The main results obtained in this work are

13、listed as follows:(1)The pristine carbon nanotubes were first acidified in nitric acid and then reacted with maleic acid, to introduce carbonyl, carboxyl and hydroxide groups onto the surface of carbon nanotubes and the final products are called Functionalized multi-walled carbon nanotubes (F-MWCNTs

14、).(2)PS/PP blends containing F-MWCNTs were prepared using a twin screw extruder followed by injection molding, the F-MWCNTs was firstly dispersed in solvent to obtain PS/F-MWCNTs master batch and then the master batch was melt blended with different contents of PP and PS to obtain samples with corre

15、sponding compositions. For the PS/PP blends without F-MWCNTs, two exothermic peaks were presented in the cooling curve of PP phase, indicating fractionated crystallization of PP. The PS/PP/F-MWCNTs nannocomposites exhibited only one exothermic peak indicating that only bulk crystallization of PP pha

16、se occurred during the cooling process. Furthermore, the nanocomposite exhibited higher crystallization temperature compared with the corresponding blends without F-MWCNTs, and the crystallization temperature shifted to higher temperatures at higher content of PP. It proved that F-MWCNTs migrated fr

17、om the PS phase to the PP phase, and nucleated the crystallization of PP. The DMA results showed that F-MWCNTs exhibited as a plasticizer for both PS and PP, decreasing the glass-transition temperature of both PP and PS in PS/PP/F-MWCNTs nanocomposites. SEM results showed that the presence of F-MWCN

18、Ts induced the morphology of the immiscible blends to change from sea-island morphology to co-continuous morphology to a certain degree.(3)Addition of maleic anhydride grafted styrene-ethylene-butylenes-styrene (SEBS-MA) as compatibilizer to 80PP/20PS blends can compatibilize the blends by reducing

19、the interfacial tension and enhancing the interfacial adhesion, and consequently result in smaller dispersed particles with better distribution. The different blending sequences and usage of compatibilizer on the selective localization of F-MWCNTs was discussed. When the F-MWCNTs were first disperse

20、d in PP and then blended with other components, the crystallization temperature of PP phase shifted to lower temperature when SEBS-MA are added, indicating the migration of F-MWCNTs to the SEBS-MA, which characterized high affinity. Due to the migration of F-MWCNTs into the SEBS-MA, less F-MWCNTs re

21、mained in the PP phase, leading to decreased temperature of PP phase. The DMA results showed that glass-transition behaviors of PS had not changed, meaning that F-MWCNTs remained on the interface instead of migrating into the PS phase. When the F-MWCNTs were first dispersed in PS and then blended wi

22、th other components to prepared the nanocomposites, the crystallization temperature of PP in different composites are nearly the same, and the DMA results showed that glass-transition behaviors of PP had not changed, indicating that the F-MWCNTs stayed in the PS phase due to obstruction of F-MWCNTs imposed by the SEBS-MA. For the 80PP-MA/20PS/SEBS-MA/F-MWCNTs nanocomposites with PS master batch, the crystallization behavior of PP-MA showed that F-MWCNTs had better affinity with SEBS-MA than PP-MA in 80PP-MA/20PS/SEBS-MA/F-MWCNTs nanocomposite.(4)The PS/PET/F-MWCNTs nanocomposi